A related art fabrication process of a silicon photovoltaic cell is described hereinbelow.
First, in order to realize high efficiency by promoting optical confinement effects, a p-type silicon substrate having a textured structure formed on a light receiving side is prepared, and subsequently subjected to a treatment at a temperature of 800 to 900° C. for several tens of minutes under a mixed gas atmosphere of phosphorus oxychloride (POCl3), nitrogen and oxygen, thereby uniformly forming an n-type diffusion layer on the substrate. According to this method of the related art, since diffusion of phosphorus is carried out using a mixed gas, the n-type diffusion layer is formed not only on the front surface, but also on the side surface and the rear surface. For these reasons, there has been a need for a side etching process to remove the n-type diffusion layer on the side surface. Further, the n-type diffusion layer of the rear surface needs to be converted into a p+-type diffusion layer, correspondingly an aluminum paste is assigned to the n-type diffusion layer of the rear surface to achieve conversion of the n-type diffusion layer into the p+-type diffusion layer through the diffusion of aluminum.
Meanwhile, in the manufacturing field of semiconductors, there has been proposed a method of forming an n-type diffusion layer by applying a solution containing phosphates such as phosphorus pentoxide (P2O5) or ammonium dihydrogen phosphate (NH4H2PO4) (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2002-75894). However, in such a method, since a solution is used, similarly to the above-stated gas-phase reaction method using a mixed gas, diffusion of phosphorus occurs at the side surface and rear surface during the formation of a diffusion layer, and an n-type diffusion layer is formed not only on the surface, but also on the side surface and the rear surface.